Magnet wire with thermoplastic insulation

ABSTRACT

Magnet wire including extruded insulation formed from multiple layers of different materials is described. A magnet wire may include a conductor and insulation formed around the conductor. The insulation may include a first layer of extruded thermoplastic insulation formed around the conductor and a second layer of extruded thermoplastic insulation formed around the first layer of extruded thermoplastic insulation. The first layer may be formed from a first polymeric material having a first thermal index, and the second layer may be formed from a second polymeric material having a second thermal index higher than the first thermal index.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.63/062,501, filed Aug. 7, 2020 and entitled “Magnet Wire withThermoplastic Insulation,” the contents of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

Embodiments of the disclosure relate generally to magnet wire and, moreparticularly, to magnet wire that includes extruded insulation formedfrom multiple layers of different materials.

BACKGROUND

Magnet wire, also referred to as winding wire or magnetic winding wire,is utilized in a wide variety of electric machines and devices, such asinverter drive motors, motor starter generators, transformers, etc.Typically, magnet wire is constructed by applying electrical insulationto a metallic conductor, such as a copper, aluminum, or alloy conductor.The insulation provides for electrical integrity and prevents shorts inthe magnet wire. Conventional insulation often consists of polymericenamel films that are applied in successive layers and cured in an oven.Enamel layers are typically applied as a varnish containing thermosetpolymeric material suspended in solvent, and the heat curing removes thesolvent. In order to achieve higher dielectric strengths and partialdischarge performance to satisfy increasing electrical performancecriteria, it is typically necessary to apply a greater number of layersand, therefore, thicken the enamel. However, each successive passthrough the baking furnace lowers the adhesive force between the enameland the conductor, and it is difficult to build the enamel thicknessbeyond a certain point. Additionally, increased enamel layering may leadto solvent blisters or beading and/or reduced flexibility. Further, theprocess for applying enamel insulation is energy intensive andinefficient, and the solvents utilized are typically hazardous materialsthat must be handled appropriately.

Recently, attempts have been made to form magnet wire insulation fromextruded thermoplastic materials. The thermoplastic insulation is eitherextruded over a bare conductor or a conductor having base enamelinsulation. For example, a relatively thick layer of a high-performancematerial, such as polyetheretherketone (“PEEK”), can be extruded over aconductor. As another example, U.S. Pat. No. 9,224,523 describes amagnet wire in which PEEK is extruded over an enamel layer. Similarly,U.S. Pat. No. 9,324,476 describes a magnet wire in which either PEEK orpolyaryletherketone (“PAEK”) is extruded over an enamel layer. The useof certain high performance thermoplastic materials can form insulationhaving similar performance to certain enamel materials. For example,PEEK may have similar performance to thermoset polyimide.

However, relatively high-performance thermoplastic materials areexpensive and increase the cost of the magnet wire relative toconventional insulation that utilizes all enamel. For example,thermoplastic PEEK may have a cost that is two to four times greaterthan thermoset polyimide. Accordingly, there is an opportunity forimproved insulated magnet wire, and more particularly, improved magnetwire that includes thermoplastic insulation formed from a plurality oflayers of different materials. In particular, there is an opportunityfor improved magnet wire that includes a base layer of a lower cost orlower performance first polymeric material and a second layer of ahigher performance second polymeric material.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items; however, various embodiments may utilize elementsand/or components other than those illustrated in the figures.Additionally, the drawings are provided to illustrate exampleembodiments described herein and are not intended to limit the scope ofthe disclosure.

FIG. 1 is a perspective view of an example magnet wire that includesextruded insulation formed from multiple layers of different materials,according to an illustrative embodiment of the disclosure.

FIGS. 2A-2D are cross-sectional views of example magnet wireconstructions that include extruded insulation formed from multiplelayers of different materials, according to illustrative embodiments ofthe disclosure.

FIG. 3 is a schematic diagram of an example system that may be utilizedto form extruded insulation on magnet wire, according to an illustrativeembodiment of the disclosure.

FIG. 4 is a flowchart depicting an example method for forming magnetwire that includes extruded insulation formed from multiple layers ofdifferent materials, according to an illustrative embodiment of thedisclosure.

DETAILED DESCRIPTION

Various embodiments of the present disclosure are directed to magnetwire that includes a conductor and insulation formed around theconductor with a plurality of layers formed from different extrudedpolymeric materials. The insulation may include at least a first layerof extruded thermoplastic insulation formed around the conductor and asecond layer of extruded thermoplastic insulation formed around thefirst layer. The first layer may be formed from a first polymericmaterial having a first thermal class, a first thermal index, and/or afirst melt temperature, and the second layer may be formed from a secondpolymeric material different than the first polymeric material andhaving a second thermal class higher than the first thermal class, asecond thermal index higher than the first thermal index, and/or asecond melt temperature higher than the first melt temperature. Incertain embodiments, the first layer of thermoplastic insulation may beformed directly around the conductor. In other embodiments, one or morebase insulation layers may be formed around a conductor, and the firstlayer of thermoplastic insulation may be formed around the baseinsulation layer(s). For example, one or more layers of polymeric enamelinsulation may be formed around a conductor, and first layer ofthermoplastic insulation may be formed around the enamel.

Other embodiments of the disclosure are directed to methods of formingmagnet wire that includes a conductor and insulation formed around theconductor that includes a plurality of different layers of extrudedthermoplastic materials. A conductor may be provided and insulation maybe formed around the conductor. Forming insulation may include forming afirst layer of thermoplastic insulation around the conductor and asecond layer of thermoplastic insulation around the first layer. Formingthe first layer may include extruding a first polymeric material havinga first thermal class, a first thermal index, and/or a first melttemperature. Forming the second layer may include extruding a secondpolymeric material different from the first polymeric material andhaving a second thermal class higher than the first thermal class, asecond thermal index higher than the first thermal index, and/or asecond melt temperature higher than the first melt temperature.

A wide variety of different polymeric materials may be utilized asdesired in various embodiments of the disclosure in order to formextruded thermoplastic insulation layers. For example, a lowerperformance and/or less expensive material may be utilized to form thefirst layer and a higher performance material may be utilized to formthe second layer. In certain embodiments, the first polymeric materialmay include at least one of polyester, copolyester, nylon, polyphenylenesulfide (“PPSU”), polyphenylsulfone (“PPS”), polyethersulfone (“PESU”),crosslinked polyethylene, polycarbonate, polystyrene, an acrylic, afluoropolymer, and/or another suitable polyolefin material. As desired,the first polymeric material may be formed from a blend or mixture of aplurality of polymeric materials. In certain embodiments, the secondpolymeric material may include at least one of polyetheretherketone(“PEEK”), polyaryletherketone (“PAEK”), or polyetherketoneketone(“PEKK”). As desired, the second polymeric material may be formed from ablend or mixture of a plurality of polymeric materials.

As desired, first and second polymeric materials may be selected basedon a wide variety of suitable properties and/or cost considerations. Incertain embodiments, the first polymeric material may have a thermalclass or a thermal index of 200° C. or less and the second polymericmaterial may have a thermal class or a thermal index of 220° C., 240°C., or more. As desired in various embodiments, one or more additivesmay be incorporated into an extruded insulation layer, suchcompatabilizers (e.g., compatabilizers utilized in a polymeric blend,etc.), filler materials, adhesion promotors, etc.

First and second layers of extruded thermoplastic insulation may also beformed with a wide variety of suitable thicknesses and ratios ofthicknesses. In certain embodiments, the first layer may constitute atleast fifty-five percent (55%), sixty percent (60%), or another suitablepercentage of a thickness of the extruded insulation (e.g., a combinedthickness of the first and second layers, etc.). For example, the firstlayer may constitute between fifty-five percent (55%) and eighty percent(80%) of a thickness of the extruded insulation and the second layer mayconstitute between twenty percent (20%) and forty-five percent (45%) ofthe thickness of the extruded insulation. Other thickness percentagesand/or ratios of thicknesses may be utilized as desired in variousembodiments. Further, the overall extruded thermoplastic insulation(e.g., the combined first and second layers, etc.) may be formed with awide variety of suitable thicknesses. In certain embodiments, theextruded thermoplastic insulation may have a thickness betweenapproximately 15 micrometers and approximately 200 micrometers, such asa thickness between 100 micrometers and 200 micrometers. Additionally,individual layers of the extruded thermoplastic insulation, such as thefirst and second layers, may be formed with any suitable respectivethicknesses.

As a result of forming extruded insulation with a plurality of layersthat include different materials, the cost of a magnet wire may bereduced relative to conventional magnet wires that utilize highperformance thermoplastic polymers, such as PEEK. For example,multi-layer insulation may include a first layer formed from a lessexpensive material and a second layer formed from a high-performancematerial, and the overall cost of the two layers may be lower than asingle layer of the high-performance material. The multi-layerinsulation may also provide similar or improved performance (e.g., PDIV,dielectric breakdown, temperature rating, etc.) relative to single layerinsulation formed from a high-performance material (e.g., PEEK).

Embodiments of the disclosure now will be described more fullyhereinafter with reference to the accompanying drawings, in whichcertain embodiments of the disclosure are shown. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. Like numbers refer to like elements throughout.

With reference to FIG. 1 , a perspective view of an example magnet wire100 that includes extruded insulation is illustrated in accordance withan embodiment of the disclosure. The magnet wire 100 may include acentral conductor 105 and insulation 110 formed around the conductor105. The insulation 110 may include at least two layers of extrudedinsulation. As shown, the insulation 110 may include a first layer 115of extruded insulation formed around the conductor 105 and a secondlayer 120 of extruded insulation formed around the first layer 115.According to an aspect of the disclosure, the first layer 115 and thesecond layer 120 may be formed from different polymeric materials (e.g.,different single materials, different groups or blends of materials,etc.). Additionally, in certain embodiments, the first layer 115 may beformed directly on the conductor 105. In other embodiments, optionalbase insulation 125 may be formed around the conductor 105, and thefirst layer 115 may be formed on the base insulation 125. As desired,the base insulation 125 may include any number of sublayers.

FIGS. 2A-2D are cross-sectional views of example magnet wireconstructions 200, 220, 250, 270 that include a plurality of differentlayers of extruded insulation, according to illustrative embodiments ofthe disclosure. FIG. 2A illustrates an example magnet wire 200 having around or circular cross-sectional shape in which multiple layers ofextruded insulation are formed around a conductor 205. For example, afirst layer 210 and a second layer 215 of extruded insulation may beformed around the conductor 205. FIG. 2B illustrates another examplemagnet wire 220 having a round cross-sectional shape. The magnet wire220 may include a conductor 225 and first and second layers 230, 235 ofextruded insulation formed around the conductor 225. However, the magnetwire 220 of FIG. 2B also includes base insulation 240 formed around theconductor 225 with the first layer 230 of extruded insulation formedaround the base insulation 240. FIG. 2C illustrates an example magnetwire 250 having a rectangular cross-sectional shape in which multiplelayers of extruded insulation are formed around a conductor 255. Forexample, a first layer 260 and a second layer 265 of extruded insulationmay be formed around the conductor 255. FIG. 2D illustrates anotherexample magnet wire 270 having a rectangular cross-sectional shape.Similar to the magnet wires 100 of FIGS. 1 and 2B, the magnet wire 270of FIG. 2D includes a conductor 275, base insulation 290 formed aroundthe conductor 275, and first and second layers 280, 285 of extrudedinsulation formed around the base insulation 290.

Each of the layers or components of the magnet wire 100 of FIG. 1 willnow be described in greater detail. The example magnet wires 200, 220,250, 270 of FIGS. 2A-2D may include layers or components similar tothose described with reference to FIG. 1 . Indeed, as desired in variousembodiments, a magnet wire may be formed with a wide variety of suitablecross-sectional shapes and insulation configurations provided that theinsulation includes a plurality of extruded insulation layer formed fromdifferent polymeric materials. The example constructions illustrated inFIGS. 1-2D are provided by way of non-limiting example only.

Turning first to the conductor 105, the conductor 105 may be formed froma wide variety of suitable materials and/or combinations of materials.For example, the conductor 105 may be formed from copper, aluminum,annealed copper, oxygen-free copper, silver-plated copper, nickel platedcopper, copper clad aluminum (“CCA”), silver, gold, a conductive alloy,a bimetal, carbon nanotubes, or any other suitable electricallyconductive material. Additionally, the conductor 105 may be formed withany suitable dimensions and/or cross-sectional shapes. As shown, theconductor 105 may have a rectangular cross-sectional shape. In otherembodiments, such as those illustrated in FIGS. 2A and 2B, a conductor105 may have a circular or round cross-sectional shape. In yet otherembodiments, a conductor may be formed with a square shape, anelliptical or oval shape, or any other suitable cross-sectional shape.Additionally, as desired for certain cross-sectional shapes such as theillustrated rectangular shape, a conductor may have corners that arerounded, sharp, smoothed, curved, angled, truncated, or otherwiseformed.

The conductor 105 may also be formed with any suitable dimensions, suchas any suitable gauge, diameter, height, width, cross-sectional area,etc. As one non-limiting example, the longer sides of a rectangularconductor 105 may be between approximately 0.020 inches (508 μm) andapproximately 0.750 inches (19050 μm), and the shorter sides may bebetween approximately 0.020 inches (508 μm) and approximately 0.400inches (10160 μm). An example square conductor may have sides betweenapproximately 0.020 inches (508 μm) and approximately 0.500 inches(12700 μm). An example round conductor may have a diameter betweenapproximately 0.010 inches (254 μm) and approximately 0.500 inches(12700 μm). Other suitable dimensions may be utilized as desired.

A wide variety of suitable methods and/or techniques may be utilized toform, produce, or otherwise provide a conductor 105. In certainembodiments, a conductor 105 may be formed by drawing input material(e.g., a larger conductor, rod stock, etc.) through one or more dies inorder to reduce the size of the input material to desired dimensions. Asdesired, one or more flatteners and/or rollers may be used to modify thecross-sectional shape of the input material before and/or after drawingthe input material through any of the dies. In certain embodiments, theconductor 105 may be formed in tandem with the application of a portionor all of the insulation system. In other words, conductor formation andapplication of insulation material may be conducted in tandem. In otherembodiments, a conductor 105 with desired dimensions may be preformed orobtained from an external source, and insulation material may then beapplied via a subsequent process.

In certain embodiments, base insulation 125 may be formed on theconductor 105 prior to application of first and second layers 115, 120of extruded insulation. A wide variety of suitable materials may beutilized as desired to form base insulation 125. For example, the baseinsulation 125 may include one or more layers of polymeric enamel, oneor more semi-conductive layers, and/or one or more tape or wrap layers.In certain embodiments, the base insulation 125 may be formed directlyon the conductor 105, for example, around an outer periphery of theconductor 105. Additionally, as desired, the base insulation 125 mayinclude a single layer of insulation material or a plurality ofsublayers of insulation material (e.g., a plurality of enamel layers,etc.).

In the event that the base insulation 125 is formed with a plurality ofsublayers, any number of sublayers may be utilized. In certainembodiments, the sublayers may be formed from the same substance ormaterial (e.g., a plurality of enamel layers formed from the samepolymeric material, etc.). In other embodiments, at least two of thesublayers may be formed from different materials. For example, differentenamel layers may be formed from different polymeric materials. Asanother example, one or more sublayers may be formed from enamel whileanother sublayer is formed from a suitable tape or wrap.

As set forth above, the base insulation 125 may include one or morelayers of enamel. An enamel layer is typically formed by applying apolymeric varnish to the conductor 105 and then baking the conductor 105in a suitable enameling oven or furnace. The polymeric varnish typicallyincludes thermoset polymeric solid material suspended in one or moresolvents. Following application of the varnish, solvent is removed as aresult of baking or curing, thereby leaving a solid polymeric enamellayer. As desired, multiple layers of enamel may be applied to theconductor 105. For example, a first layer of enamel may be applied, andthe conductor 105 may be passed through an enameling oven or othersuitable curing device. A second layer of enamel may then be applied,and the conductor 105 may make another pass through the curing device(or a separate curing device). This process may be repeated until adesired number of enamel coats have been applied and/or until a desiredenamel thickness or build has been achieved. As desired, an enamelingoven may be configured to facilitate a wire 100 making multiple passesthrough the oven. Other curing devices that may be utilized in additionto or as an alternative to enameling ovens include, but are not limitedto, infrared light systems, ultraviolet light systems, and/or electronbeam systems.

Any number of enamel layers may be formed in various embodiments.Additionally, each layer of enamel and/or a total enamel build may haveany desired thickness, such as a thickness of approximately 0.0002,0.0005, 0.007, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008,0.009, 0.010, 0.012, 0.015, 0.017, or 0.020 inches, a thickness includedin a range between any two of the aforementioned values, or a thicknessincluded in a range bounded on either a minimum or maximum end by one ofthe aforementioned values. A wide variety of different types ofpolymeric materials may be utilized as desired to form an enamel layer.Examples of suitable materials include, but are not limited to,polyimide, polyamideimide, amideimide, polyester, polyesterimide,polysulfone, polyphenylenesulfone, polysulfide, polyphenylenesulfide,polyetherimide, polyamide, polyketones, etc. In certain embodiments, thebase insulation 125 may include polyimide (“PI”) enamel, polyamideimide(“PAI”) enamel, or a combination thereof. As desired, one or moresuitable filler materials may be incorporated into an enamel layer.Examples of suitable filler materials include, but are not limited to,inorganic materials (e.g., metals, etc.), organic materials, and/orother materials, such as any of the filler materials described belowwith reference to the extruded insulation layers. In certainembodiments, the filler material(s) may enhance corona resistance and/orone or more thermal properties (e.g., temperature resistance,cut-through resistance, heat shock, etc.) of an enamel layer. Theparticles of a filler material may have any suitable dimensions, such asany suitable diameters. Further, any suitable blend or mixture ratiobetween filler material and the polymeric material of an enamel layermay be utilized.

As desired, other types of base insulation 125 may be utilized inaddition to or as an alternative to enamel. In certain embodiments, thebase insulation 125 may include one or more suitable wraps or tapes,such as a polymeric tape wrapped around the conductor 105 and/or anyunderlying layers. In other embodiments, the base insulation 125 mayinclude one or more semi-conductive layers of material. Asemi-conductive layer may have a conductivity between that of aconductor 105 and that of an insulator, and the use of one or moresemi-conductive layers may assist in equalizing or “smoothing out”non-uniform electric, magnetic, and/or electromagnetic fields that maystress the magnet wire insulation.

With continued reference to FIG. 1 , the insulation 100 may include aplurality of layers of extruded insulation formed around the conductor105. According to an aspect of the disclosure, at least a first layer115 of extruded insulation may be formed around the conductor 105, and asecond layer 120 of extruded insulation may be formed around the firstlayer 115. Additionally, the first and second layers 115, 120 may beformed from different thermoplastic polymeric materials. For example,the first layer 115 may be formed with a lower performance and/or lowercost material than the second layer 120. In certain embodiments, such asthe embodiments illustrated in FIGS. 2A and 2D, the first layer 115 ofextruded insulation may be formed directly around the conductor 105without any intervening insulation layers. In other embodiments, such asthe embodiments illustrated in FIGS. 1, 2B and 2D, the first layer 115of extruded insulation may be formed over base insulation 125 (e.g.,polymeric enamel, etc.).

A wide variety of suitable materials and/or combinations of materialsmay be utilized to form extruded insulation, such as the first layer 115and the second layer 120. Examples of suitable materials include, butare not limited to, polyetheretherketone (“PEEK”), polyetherketoneketone(“PEKK”), polyetheretherketoneketone (“PEEKK”), polyetherketone (“PEK”),polyaryletherketone (“PAEK”), other suitable polymers that include atleast one ketone group, polyetherimide (“PEI”) such as Ultem® marketedby Sabic Global Technologies, polyphenylsulfone (“PPSU”) such as Radel®marketed by Solvay Specialty Polymers USA, polyethersulfone (“PESU”),polyphenylene sulfide (“PPS”), polybenzimidazole (“PBI”), polycarbonate,one or more polyesters (e.g., polyethylene terephthalate (“PET”), etc.),one or more copolyesters, nylon, thermoplastic polyamide, thermoplasticpolyimide (“TPI”), one or more acrylic materials, one or morefluoropolymers, polystyrene, and/or various copolymers of multiplematerials.

In certain embodiments, a first layer 115 may be formed from a lowerperformance and/or less expensive material, and a second layer 120 maybe formed from a higher performance material. In certain exampleembodiments, the first layer 115 may me formed from a firstthermoplastic polymeric material that includes at least one ofpolyester, copolyester, nylon, polycarbonate, acrylic, a fluoropolymer,polyphenylene sulfide (“PPSU”), polyethersulfone (“PESU”),polyetherimide (“PEI”), or polyphenylsulfone (“PPS”). The second layer120 may be formed from a second thermoplastic polymeric material thatincludes at least one of polyetheretherketone (“PEEK”),polyaryletherketone (“PAEK”), or polyetherketoneketone (“PEKK”). Incertain embodiments, one of the first layer 115 or the second layer 120may be formed from a blend or mixture of a plurality of polymericmaterials. For example, the first layer 115 may be formed from apolymeric blend that includes at least one of the example materialslisted above as suitable for the first layer 115. As another example,the second layer 120 may be formed from a polymeric blend that includesat least one of the materials listed above as suitable for the secondlayer 120 (e.g., a blend including PEEK, etc.). Additionally, in certainembodiments, the polymeric material(s) utilized to form the first layer115 may be immiscible with the polymeric material(s) utilized to formthe second layer 120.

In one example embodiment, a first layer 115 may be formed from PEI anda second layer 120 may be formed from PEEK. In another exampleembodiment, a first layer 115 may be formed from PEI and a second layermay be formed from PAEK. In another example embodiment, a first layermay be formed from PEI and a second layer may be formed from PEKK. Inother example embodiments, a first layer may be formed from PPSU and asecond layer may be formed from PEEK, PAEK, or PEKK. In other exampleembodiments, a first layer may be formed from PESU and a second layermay be formed from PEEK, PAEK, or PEKK. In yet other exampleembodiments, a first layer may be formed from PSU and a second layer maybe formed from PEEK, PAK, or PEKK. Other layer combinations may beutilized as desired.

Although example extruded insulation is described herein as having afirst layer 115 and a second layer 120, extruded insulation may beformed with any number of suitable layers. For example, in otherembodiments, three or more layers of extruded material may beco-extruded or otherwise incorporated into an insulation system. Forexample, a combination of PPSU, PEI, and PEEK may be co-extruded astriple layer insulation. Other suitable combinations of materials,including any of the materials discussed herein, can alternatively beutilized to form three or more co-extruded insulation layers.

In the event that an extruded layer (e.g., the first layer 115, thesecond layer 120, etc.) is formed from a polymeric material that is ablend, two or more component polymeric materials may be blended or mixedtogether at any suitable blend rates or ratios within the blend. Forexample, each component material may constitute between approximately1.0% and approximately 99% by weight of a polymeric blend. In certainembodiments, each component material incorporated into a blend (e.g., afirst component material, a second component material, etc.) mayconstitute approximately 5, 10, 15, 20, 25, 30, 40, 45, 50, 60, 70, 75,80, 90, or 95% by weight of the blend, a weight percentage included in arange between any two of the above values (e.g., between approximately 5and 95%, between approximately 10 and 90%, etc.), or a weight percentageincluded in a range bounded on either a minimum or maximum end by one ofthe above values (e.g., at least 5%, at least 10%, no more than 95%, nomore than 90%, etc.). Component materials and relative amounts ofmaterials incorporated into a blend may be selected based on a widevariety of suitable factors including, but not limited to, costs of thematerials, processing characteristics, desired dielectric breakdown,desired partial discharge inception voltage (“PDIV”), desired cutthrough, desired thermal aging properties, desired temperature rating,desired crystallinity, etc.

As desired, first and second polymeric materials respectively utilizedto form the first layer 115 and the second layer 120 may be selectedbased on a wide variety of suitable properties and/or costconsiderations. For example, the first polymeric material may have afirst melt point (or melting point) that is lower than a second meltpoint of the second polymeric material. In certain embodiments, thefirst polymeric material may have a melt point that is lower than 300°C., 250° C., 200° C., 180° C., or another suitable value. The secondpolymeric material may then have a melt point that is higher than thatof the first polymeric material. Similarly, in certain embodiments, thefirst polymeric material may have a first glass transition temperaturethat is lower than a second glass transition temperature of the secondpolymeric material. In certain embodiments, the first polymeric materialmay have a glass transition temperature that is lower than 300° C., 250°C., 200° C., 180° C., or another suitable value. The second polymericmaterial may then have a glass transition temperature that is higherthan that of the first polymeric material.

In various embodiments, the first and second polymeric materials may beselected to have different thermal classifications (or thermal classes),thermal indexes, or thermal endurances. In other words, the firstpolymeric material may have a first thermal class, thermal index, orthermal endurance that is lower than a second thermal class, thermalindex, or thermal endurance of the second polymeric material. Thermalclasses, which are generally established by industry standardsorganizations (e.g., the National Electric Manufacturers Association,the International Electrotechnical Commission, UL, etc.), establishmaximum allowable temperatures for an insulation material and/or magnetwire. Example thermal classes include, for example, 180° C., 200° C.,220° C., 240° C., and 250° C. A thermal index is generally defined as anumber in degrees Celsius that compares the temperature vs. timecharacteristics of an electrical insulation material. It may be obtainedby extrapolating the Arrhenius plot of life versus temperature to aspecified time, usually 20,000 hours. As an example of the differencebetween a thermal class and a thermal index, a material may have athermal index of 230° C.; however, that material will have a thermalclass of 220° C. as it does not meet the requirements of the nextavailable thermal class of 240° C. In certain embodiments, the firstpolymeric material may have a thermal class of 200° C. or less and thesecond polymeric material may have a thermal class of 220° C. or more.In other embodiments, the first polymeric material may have a thermalclass of 200° C. or less and the second polymeric material may have athermal class of 240° C. or more. In one example embodiment, a firstpolymeric material may be a PPSU material having a thermal class of 200°C., and a second polymeric material may be a PEEK material having athermal class of 240° C. or more. In other embodiments, the first andsecond polymeric materials may be selected to have different thermalindexes. In other words, the first polymeric material may have a firstthermal index that is lower than a second thermal index of the secondpolymeric material. For example, the first polymeric material may have athermal index of 200° C. or less, and the second polymeric material mayhave a thermal index greater than or equal to 220° C., 225° C., 230° C.,235° C., 240° C., 245° C., 250° C., 255° C., 260° C., or a thermal indexincluded in a range between any two of the above values.

Additionally, in certain embodiments, the first and second polymericmaterials may be selected to have different physical properties. Forexample, the first polymeric material may include an amorphous materialand the second polymeric material may include a semi-crystalline or acrystalline material. Thermoplastic materials with a semi-crystallinestructure may provide desirable mechanical properties and/or desirablechemical resistance due to the unique crystal structure inside thematerial. However, a semi-crystalline material typically exhibits ahigher thermal expansion and shrinkage ratio during processing. Forinstance, PEEK has an average mold shrinkage between approximately 1.1and 1.5. This shrinkage is higher than amorphous materials, such as PPSUwhich has a mold shrinkage ratio of approximately 0.7. The higher moldshrinkage ratio of semi-crystalline materials may generate greaterresidual stress during the wire extrusion process, which may lead torelatively low adhesion properties. This problem is exacerbated forthicker build extruded magnet wires. Using multiple layers of extrudedmaterial in accordance with embodiments of the present disclosure canimprove the adhesion properties of the extruded insulation while stillallowing the extruded insulation (e.g., an outer layer ofsemi-crystalline material, etc.) to provide desired mechanicalproperties, desired chemical resistance, and/or desired thermalproperties. Additionally, if the materials utilized to form multiplelayers of extruded insulation have similar volume resistances anddielectric constants, the dielectric properties and electricalperformance of the multi-layer insulation may be similar or better thanthat of extruded insulation formed from a single material (e.g., PEEK,etc.).

As desired in various embodiments, one or more additives may beincorporated into an extruded insulation layer, such as the first layer115 and/or the second layer 120. For example, in certain embodiments,one or more compatabilizers may be added to a polymeric material or apolymeric blend in order to increase the stability of the material orpolymeric blend. As another example, one or more fluoropolymers, such aspolytetrafluoroethylene (“PTFE”) may be blended, mixed, added, orotherwise incorporated into an extruded insulation layer. As yet anotherexample, one or more suitable filler materials may be added to apolymeric material utilized to form an extruded insulation layer.Examples of suitable filler materials include, but are not limited to,inorganic materials such as metals, transition metals, lanthanides,actinides, carbon nanotubes, boron nitride, metal oxides, and/orhydrated oxides of suitable materials such as aluminum, tin, boron,germanium, gallium, lead, silicon, titanium, chromium, zinc, yttrium,vanadium, zirconium, nickel, etc. (e.g., titanium dioxide, silica orsilicon dioxide, etc.); suitable organic materials such as polyaniline,polyacetylene, polyphenylene, polypyrrole, other electrically conductiveparticles; and/or any suitable combination of materials (e.g., a blendof metal oxides, etc.). In certain embodiments, the filler material(s)may enhance corona resistance and/or one or more thermal properties(e.g., temperature resistance, cut-through resistance, heat shock,etc.). In certain embodiments, a filler material may include at leastone of titanium dioxide, chromium dioxide, silica dioxide, or boronnitride. The particles of a filler material may have any suitabledimensions, and any suitable blending ratio or fill rate between fillermaterial and polymeric materials may be utilized (e.g., a fill rate ofapproximately 5, 10, 15, 20, or 25 percent, or a fill rate included in arange between any of these values). Additionally, in the event that afiller includes a blend of different materials, any suitable blendingratio may be utilized between the components of the filler.

In certain embodiments, a tie layer or adhesion promoting layer may beformed between the first layer 115 and the second layer 120. A widevariety of suitable materials and/or combinations of materials may beutilized as desired to form a tie layer including, but not limited to,polyester, polyurethane, and/or polymeric materials that incorporate oneor more adhesion promoters. As desired, the tie layer may be extruded orotherwise formed between the first layer 115 and the second layer 120.The use of a tie layer or adhesive promoting layer may permit a widevariety of different polymeric materials to be utilized for the firstlayer 115 and the second layer 120.

The first and second layers 115, 120 of extruded thermoplasticinsulation may also be formed with a wide variety of suitablethicknesses and ratios of thicknesses. In certain embodiments, the firstlayer 115 may constitute at least fifty-five percent (55%) of athickness of the extruded insulation (e.g., a combined thickness of thefirst and second layers 115, 120, etc.). In other embodiments, the firstlayer 115 may constitute between fifty-five percent (55%) and eightypercent (80%) of a thickness of the extruded insulation and the secondlayer 120 may constitute between twenty percent (20%) and forty-fivepercent (45%) of the thickness of the extruded insulation. In yet otherembodiments, the first layer 115 may constitute between fifty-fivepercent (55%) and ninety percent (90%) of a thickness of the extrudedinsulation (or total insulation) and the second layer 120 may constitutebetween ten percent (10%) and forty-five percent (45%) of the thicknessof the extruded insulation. Other thickness percentages and/or ratios ofthicknesses may be utilized as desired in various embodiments. Forexample, the first layer 115 may constitute at least 51, 55, 60, 65, 70,75, 80, 85, 90, or 95% of the total thickness of the extrudedinsulation, or a thickness included in a range between any two of theabove values. The second layer 120 may constitute approximately 5, 10,15, 20, 25, 30, 35, 40, 45, or 49% of the total thickness, a thicknessincluded in a range bounded on a maximum end by one of the above values,or a thickness included in a range between two of the above values.

Additionally, in certain embodiments, a wide variety of suitablethickness ratios may be utilized between the first layer 115 and thesecond layer 120. In various example embodiments, a thickness ratiobetween the first layer 115 and the second layer 120 may beapproximately 99/1, 95/5, 90/10, 85/15, 80/20, 75/25, 70/30, 60/40,55/45, 51/49, ora ratio included in a range between any two of the abovevalues.

The examples above describe magnet wires in which a first layer 115 ofextruded polymer material is thicker than a second layer 120 ofhigh-performance material. It was found that desired insulationperformance can be achieved with a thicker first layer 115 whilemaximizing or enhancing the cost of a magnet wire. In other embodiments,a magnet wire may be formed with two extruded layers in which the firstlayer 115 is thinner than the second layer 115. For example, the firstlayer 115 may constitute approximately 5, 10, 15, 20, 25, 30, 35, 40,45, or 49% of the total thickness of the first and second layers, athickness included in a range between any two of the above values, or athickness included in a range bounded on a maximum end by one of theabove values. The second layer 120 may constitute approximately 51, 55,60, 65, 70, 75, 80, 85, 90, or 95% of the total thickness of theextruded insulation, a thickness included in a range between any two ofthe above values, or a thickness included in a range bounded on aminimum end by one of the above values. Similarly, a wide variety ofsuitable thickness ratios may be utilized between the first layer 115and the second layer 120. In various example embodiments, a thicknessratio between the first layer 115 and the second layer 120 may beapproximately 1/99, 5/95, 10/90, 15/85, 20/80, 25/75, 30/70, 40/60,45/55, 49/51, or a ratio included in a range between any two of theabove values. In yet other embodiments, the first layer 115 and thesecond layer 120 may be formed with approximately equal thicknesses(e.g., an approximately 50/50 thickness ratio, etc.).

Although the respective first and second layers 115, 120 are illustratedin FIG. 1 as single layers, in other embodiments, one or both of thefirst and second layers 115, 120 may be formed from a plurality ofsublayers. As a result, more than two individual layers of extrudedthermoplastic insulation may be included in the insulation 110 of a wire100. In certain embodiments, a plurality of lower cost or lowerperformance thermoplastic materials may be utilized to form sublayers ofthe first layer 115. In certain embodiments, a plurality of sublayersincorporated into an extruded layer, such as the first layer 115 or thesecond layer 120, may be formed from the same polymeric material (e.g.,a single polymer material, a polymeric blend, etc.). In otherembodiments, at least two sublayers may be formed from differentpolymeric materials. In one example embodiment, a first sublayer formedfrom a first material may provide greater adhesion to an underlyinglayer (e.g., the conductor 105, base insulation 125, an underlying firstlayer 115), and a second sublayer formed from a second material mayprovide other desirable properties (e.g., electrical performance,mechanical performance, fluid resistance, etc.). In another exampleembodiment, a first sublayer may be formed as a filled layer while asecond sublayer (either formed from the same polymeric material or adifferent polymeric material) is unfilled. Indeed, a wide variety ofsublayer configurations may be utilized as desired for either the firstlayer 115 or the second layer 120. As a result, it will be appreciatedthat any suitable number of layers of extruded insulation may beincorporated into a magnet wire 100.

Further, the overall extruded thermoplastic insulation (e.g., thecombined first and second layers 115, 120, etc.) may be formed with awide variety of suitable thicknesses. In certain embodiments, theextruded thermoplastic insulation may have a thickness betweenapproximately 15 micrometers and approximately 200 micrometers. In otherembodiments, the extruded thermoplastic insulation may have a thicknessbetween 100 micrometers and 200 micrometers. In various embodiments, theoverall extruded thermoplastic insulation may have a thickness ofapproximately 15, 20, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250,275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, or 600micrometers, a thickness included in a range between any two of theabove values, or a thickness included in a range bounded on either aminimum or maximum end by one of the above values. Additionally,individual layers of the extruded thermoplastic insulation, such as thefirst and second layers 115, 120, may be formed with any suitablerespective thicknesses.

These example thicknesses allow the extruded insulation to be thinenough to allow a relatively tight packing of the resulting magnet wire100. Additionally, in certain embodiments, the extruded insulation maybe formed to have a cross-sectional shape that is similar to that of theunderlying conductor 105 and/or any base insulation 125. For example, ifthe conductor 105 has a rectangular cross-sectional shape, the extrudedinsulation may be formed to have a rectangular cross-sectional shape. Inother embodiments, the extruded insulation may be formed with across-sectional shape that varies from that of the underlying conductor105 (and/or the underlying base insulation 125). As one non-limitingexample, the conductor 105 may be formed with an ellipticalcross-sectional shape while the extruded insulation is formed with arectangular cross-sectional shape. A wide variety of other suitableconfigurations will be appreciated.

An extrusion process may result in the formation of extruded insulationlayers (e.g., the first and second layers 115, 120) from approximately100% solid material. In other words, the extruded insulation layers maybe free or substantially free of any solvents. As a result, theapplication of the extruded insulation layers may be less energyintensive than the application of an enamel layer as there is no need toevaporate solvents. In certain embodiments, the first and second layers115, 120 may be formed simultaneously. In other words, a singlepolymeric extrusion step may be performed during which the first andsecond layers 115, 120 are co-extruded around the conductor 105. Inother embodiments, the first and second layers 115, 120 may be formedvia a plurality of separate or serial extrusion steps or operations. Inother words, the first layer 115 may be extruded, and the second layer120 may subsequently be extruded over the first layer 115. Any number ofextrusion steps or operations may be performed as desired to constructthe first and second layers 115, 120, as well as any sublayers thereof.

In certain embodiments, an extrusion process may be controlled such thatthe extruded first and second layers 115, 120 have relatively uniformthicknesses along a longitudinal length of the magnet wire 100. In otherwords, the extruded insulation and/or one or more extruded layers (e.g.,the first layer 115, the second layer 120) may be formed with aconcentricity that is approximately close to 1.0. The concentricity ofthe extruded insulation (or an extruded layer) is the ratio of thethickness of the extruded insulation to the thinness of the extrudedinsulation at any given cross-sectional point along a longitudinallength of the magnet wire 100. In certain embodiments the extrudedinsulation (or an extruded layer) may be formed with a concentricitybetween approximately 1.0 and 1.8. For example, the extruded insulation(or an extruded layer) may be formed with a concentricity ofapproximately 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5,1.6, 1.7, 1.75, 1.8, a concentricity between any two of the abovevalues, or a concentricity bounded on a maximum end by one of the abovevalues (e.g., a concentricity of approximately 1.1 or less, aconcentricity of approximately 1.3 or less, etc.). Similar to theextruded insulation layers, application of one or more other insulationlayers (e.g., a layer of base insulation 125, etc.) may also becontrolled to result in a desired concentricity, such as any of theexample concentricities discussed above with reference to the extrudedinsulation.

As discussed above, in certain embodiments, the first layer 115 may beformed directly on the conductor 105 or the underlying base insulation125. In other words, the first layer 115 may be formed on an underlyinglayer without the use of a bonding agent, adhesion promoter, or adhesivelayer. For example, the first layer 115 may be formed from a polymericmaterial that provides a desired adhesion. As another example, thetemperature of the magnet wire 100 may be controlled prior to theapplication of the first layer 115 to eliminate the need for an adhesivelayer. As a result, the first layer 115 may be bonded to an underlyinglayer without use of a separate adhesive. In other embodiments, one ormore suitable bonding agents, adhesion promoters, or adhesive layers maybe incorporated between the first layer 115 and an underlying layer. Awide variety of suitable adhesion promoters may be utilized as desired.Similarly, in certain embodiments, the second layer 120 may be formeddirectly on the first layer 115. In other embodiments, one or moresuitable bonding agents, adhesion promoters, or adhesive layers may beincorporated between the first layer 115 and the second layer 120.Similarly, bonding agents, adhesion promoters, and/or adhesive layersmay optionally be incorporated between various sublayers of an extrudedlayer.

In other embodiments, one or more suitable surface modificationtreatments may be utilized on a conductor 105, any number of baseinsulation 125 layers, and/or any number of extruded layers to promoteadhesion with a subsequently formed layer. For example, a surface of aconductor, enamel, base layer, or extruded layer may be modified by asuitable treatment in order to promote adhesion with a subsequentlyformed insulation layer (e.g., a subsequently formed enamel layer, asubsequently formed extruded layer, etc.). Examples of suitable surfacemodification treatments include, but are not limited to, a plasmatreatment, an ultraviolet (“UV”) treatment, a corona dischargetreatment, and/or a gas flame treatment. A surface treatment may alter atopography of a conductor or insulation layer and/or form functionalgroups on the surface of the conductor or insulation layer that enhanceor promote bonding of a subsequently formed insulation layer. As aresult, surface treatments may reduce interlayer delamination.

As a result of forming extruded insulation with a plurality of layers(e.g., the first layer 115 and the second layer 120) that includedifferent materials, the cost of a magnet wire 100 may be reducedrelative to conventional magnet wires that utilize high-performancethermoplastic polymers, such as PEEK. For example, multi-layerinsulation may include a first layer 115 formed from a less expensivematerial and a second layer 120 formed from a high-performance material,and the overall cost of the two layers 115, 120 may be lower than asingle layer of the high-performance material (e.g., all PEEK, etc.).The multi-layer extruded insulation may also provide similar performanceor, in some cases, better performance (e.g., PDIV, dielectric breakdown,temperature rating, etc.) relative to single layer insulation formedfrom a high-performance material (e.g., PEEK).

Extruded insulation formed with a plurality of layers includingdifferent materials and/or an insulation system that incorporates theextruded insulation may have a wide variety of suitable electricalperformance parameters, such as a wide variety of suitable PDIV valuesand/or dielectric strength or breakdown strength values. In certainembodiments, multi-layer extruded insulation and/or an insulation systemincorporating the multi-layer extruded insulation may provide a PDIVvalue at 25° C. of at least approximately 1000, 1100, 1200, 1250, 1300,1350, 1400, 1450, 1500, 1550, 1600, 1700, 1800, 1900, 2000, 2100, 2200,2300, or 2400 volts, or a PDIV value included in a range between any twoof the above values. Similarly, in certain embodiments, extrudedinsulation and/or an insulation system incorporating the extrudedinsulation may provide a dielectric strength value (e.g., a dielectricstrength value measured by a suitable industry standard test such as ashotbox or foil test, etc.) of at least approximately, 10,000, 11,000,12,000, 12,500, 13,000, 13,500, 14,000, 14,500, 15,000, 15,500, 16,000,16,500, 17000, 17,500, 18,000, 18.500, 19,000, 20,000, 20,500, or 21,000volts, or a dielectric strength value included in a range between anytwo of the above values. In certain embodiments, the polymeric materialsutilized to form the first layer 115 and the second layer 120 may beselected in order to achieve desired electrical (e.g., PDIV, dielectricstrength, etc.) and/or chemical resistance properties for intendedmagnet wire applications.

The magnet wires 100, 200, 220, 250, 270 described above with referenceto FIGS. 1-2D are provided by way of example only. A wide variety ofalternatives could be made to the illustrated magnet wires 100, 200,220, 250, 270 as desired in various embodiments. For example, a widevariety of different types of insulation layers may be incorporated intoa magnet wire in addition to extruded insulation formed from a polymericblend. As another example, the cross-sectional shape of a magnet wireand/or one or more insulation layers may be altered. Indeed, the presentdisclosure envisions a wide variety of suitable magnet wireconstructions.

A wide variety of suitable systems and/or methods may be utilized asdesired to form multiple layers of extruded insulation on a magnet wire,such as any of the example magnet wires of FIGS. 1-2D. A schematicdiagram of one example system 300 for forming multiple layers ofextruded insulation is illustrated in FIG. 3 . The system 300 mayinclude a wide variety of components that facilitate processing a magnetwire 305. As shown, the system 300 may include a pay-off 310, apreheater 315, an extruder 320, a cooling trough 325, and a take-off330. Each of these components, as well as other components that mayoptionally be incorporated into the system 300, are described in greaterdetail below.

With reference to FIG. 3 , a suitable pay-off 310 may provide a magnetwire 305 to components of the system 300 configured to form extrudedinsulation. In certain embodiments, the pay-off 310 may provide magnetwire 305 having desired dimensions (e.g., a desired cross-sectionalshape, a desired diameter, a desired width and thickness, etc.). Asdesired, base insulation may also be formed on the magnet wire 305 priorto the pay-off 310 providing the magnet wire 305. In other embodiments,the pay-off 310 may provide input material to one or more componentsconfigured to form a conductor having desired dimensions and/or to oneor more components configured to form base insulation.

As desired, the system 300 may include one or more wire forming devicesor components configured to receive input material (e.g., rod stock,etc.) and process the received input material to form a conductor withdesired dimensions. For example, input material may be processed by asuitable rod breakdown device or rod mill that draws or pulls inputmaterial through one or more dies that reduce the size of the inputmaterial to desired dimensions. As desired, one or more flattenersand/or rollers may be used to modify the cross-sectional shape of theinput material (e.g., to form rectangular wire). As another example,input material may be processed by a suitable conform device or systemthat forms a conductor having desired dimensions. As yet anotherexample, a conductor may be formed via a 3D printing or additivemanufacturing process.

In certain embodiments, the system 300 may include one or morecomponents or subsystems configured to form base insulation on themagnet wire 305 prior to the formation of extruded insulation. Forexample, the system 300 may include one or more enamel formationcomponents, such as a varnish application system (e.g., an applicationdie, etc.) and one or more curing devices (e.g., an enameling oven, anultraviolet curing system, etc.) configured to form any suitable numberof enamel layers on the magnet wire 305. Other suitable base insulationformation components may be incorporated into the system 300 as desired.

With continued reference to FIG. 3 , the system 300 may include one ormore components configured to control the temperature of magnet wire 305prior to the application of extruded insulation. For example, the magnetwire 305 may be passed through one or more preheaters 320 in order toattain a desired temperature prior to an extrusion process. A preheater315 may include any suitable components configured to increase or raisethe temperature of the magnet wire 305, such as one or more heatingcoils, heaters, ovens, etc. As necessary, one or more cooling devicesmay also be utilized. The temperature of the magnet wire 305 may beadjusted or controlled to achieve a wide variety of suitable valuesprior to extrusion. For example, in certain embodiments, the temperaturemay be controlled to approximately, 180° C. or greater, 200° C. orgreater, or another desired temperature prior to extrusion. As anotherexample, temperature may be controlled to approximately 400° F. orgreater prior to extrusion. Controlling or maintaining the temperatureat this level may facilitate adhesion between the extruded thermoplasticlayer and the underling conductor or base insulation.

One or more suitable extruders 320 or extrusion devices may beconfigured to receive the magnet wire 305 and extrude multiple layers ofthermoplastic insulation on the magnet wire 305. In certain embodiments,the extruder(s) 320 may be configured to co-extrude both a first layerand a second layer of extruded thermoplastic insulation. In otherembodiments, the extruder(s) 320 may be configured to serially orsuccessively apply the first layer and the second layer of extrudedthermoplastic insulation. In certain embodiments, each extruder 320 maybe a single screw or a multi-screw (e.g., dual screw, etc.) extruderconfigured to receive input material and process (e.g., mix, increasethe temperature, increase the pressure, etc.) the input material priorto extrusion onto the magnet wire 305 by any number of suitableextrusion heads and/or other devices configured to apply a desiredamount of thermoplastic insulation. As desired, the flow rates of theextruded insulation may be controlled in order to obtain a desiredthickness. Additionally, in certain embodiments, one or more extrusiondies may be utilized to control the thickness and/or shape of theextruded insulation.

A wide variety of suitable operations may be performed in order tofacilitate and/or optimize the co-extrusion of a plurality of layers ofthermoplastic insulation, such as first and second layers of extrudedinsulation. In certain embodiments, the melt temperatures and/orviscosities of one or more extruded materials may be adjusted in orderto optimize the compatibility and/or adhesion of the extruded materials.In certain embodiments, the conductor temperature may also be adjustedin order to optimize compatibility and/or adhesion of one or moreextruded materials.

With continued reference to FIG. 3 , the system 300 may include anysuitable devices configured to control the temperature of the magnetwire 305 following the extrusion process. In certain embodiments, theextruded insulation may be heated following extrusion. Additionally, incertain embodiments, the process of cooling the extruded insulationprior to taking up the finished magnet wire 305 may be controlled. As aresult of controlling the cooling rate of the extruded insulation,desirable characteristics (e.g., a desired crystallinity, etc.) may beachieved. Cooling devices may include any suitable devices and/orsystems configured to lower the temperature of the finished magnet wireprior to take-up (or subsequent processing). In certain embodiments, thecooling devices may include a cooling trough 325, quencher, or liquidbath (e.g., a water bath) through which the magnet wire 305 may bepassed in order to cool. The temperature of the liquid in the bath maybe controlled via recycling liquid. Additionally, the cooling rate maybe controlled as a function of controlling the liquid temperature and/orestablishing a desired length of the cooling trough 325.

Following cooling of the extruded insulation, the finished magnet wire305 may be provided to one or more suitable take-offs 330, accumulators,or take-up devices. These devices may, for example, apply tension to themagnet wire 305, bundle the wire 305, and/or wind the finished wire 305onto a spool. In other embodiments, the magnet wire 305 may be providedto one or more downstream devices or components prior to take-off. Forexample, the magnet wire 305 may be provided to one or more componentsconfigured to form additional insulation on the magnet wire 305, such asa subsystem configured to form a conformal insulation layer (e.g., aparylene layer, etc.) on the magnet wire 305. As another example, themagnet wire 305 may be provided to one or more components configured toform one or more articles from the magnet wire 305, such as hairpins orcoils that may be incorporated into a motor or other electricalappliance.

In certain embodiments, formation of the first and second layers ofextruded insulation may be formed in a tandem or inline manner with oneor more other processes. For example, formation of the extrudedinsulation may be formed in a tandem manner with wire drawing orconductor formation and/or with the formation of one or more baseinsulation layers. In other embodiments, the magnet wire 105 may betaken up at any suitable steps within the overall process andsubsequently provided to another component or subsystem.

Additionally, any suitable number of motors, flyers, capstans, and/orload cells may be incorporated into the system 300 to control passage ofmagnet wire 305 through the system 300. Any suitable number ofcontrollers (e.g., control units, computers, microcontrollers, etc.) maybe configured to control various components of the system 300. Forexample, one or more controllers may facilitate synchronization ofmotors and/or line speeds within the system 300. As desired, acontroller and/or combination of controllers may additionally control awide variety of other parameters, such as the flow rate of an appliedvarnish, the temperature of an enameling oven, the temperature ofvarious heating/cooling devices, the flow rate of an extrusion device,the temperature of liquid included in a quencher, and/or various testingconducted on the magnet wire 305. Each controller may be a separatecomponent or, alternatively, incorporated into another device orcomponent. Additionally, any number of suitable communications channels(e.g., wired communications channels, wireless communications channels,etc.) may facilitate communication between a controller and one or moreother components (e.g., one or more motors, another controller, otherdevices, etc.).

The system 300 described above with reference to FIG. 3 is provided byway of example only. A wide variety of other suitable systems may beutilized to form a magnet wire that includes multiple layers of extrudedinsulation. These systems may include more or less components than thesystem 300 of FIG. 3 . Additionally, these systems may include certainalternative components to the system 300 of FIG. 3 , which is providedby way of non-limiting example only. Indeed, the present disclosureenvisions a wide variety of suitable systems that may be utilized toform magnet wire.

FIG. 4 is a flowchart depicting an example method 400 for forming magnetwire that includes multiple layers of extruded insulation, according toan illustrative embodiment of the disclosure. The method 400 may beperformed utilizing a wide variety of suitable systems and/or devices.For example, a portion of the method 400 may be performed by the system300 of FIG. 3 . The method 400 may begin at block 405, and a conductormay be provided. In certain embodiments, a preformed conductor havingdesired dimensions may be provided. In other embodiments, input materialmay be provided and processed in order to form a conductor havingdesired dimensions. For example, input material may be processed by arod mill, flatteners, and/or rollers in order to provide a conductorhaving desired dimensions.

At block 410, which is optional in certain embodiments, base insulationmay be formed on the conductor. A wide variety of suitable baseinsulation and/or combinations of different types of base insulation maybe formed as desired. For example, one or more enamel layers may beformed. In certain embodiments, one or more layers of polyamideimideand/or polyimide enamel may be formed as base insulation. As anotherexample, one or more semi-conductive layers may be formed.

At block 415, first and second thermoplastic polymeric materials may beprovided for extrusion. As set forth herein, a wide variety of suitablematerials, combinations of materials, and/or polymeric blends may beprovided as first and second polymeric materials. According to an aspectof the disclosure, the first polymeric material may be different fromthe second polymeric material, and the materials may have differentproperties, such as different thermal indexes, thermal classes, meltpoints, glass transition temperatures, etc. In certain embodiments, afirst thermoplastic polymeric material may include at least one ofpolyester, nylon, polyphenylene sulfide (“PPSU”), or polyphenylsulfone(“PPS”). A second thermoplastic polymeric material may include at leastone of polyetheretherketone (“PEEK”), polyaryletherketone (“PAEK”), orpolyetherketoneketone (“PEKK”). Other suitable materials may be providedas desired. Additionally, a wide variety of fillers, compatabilizers,and/or other suitable additives may be incorporated into a polymericmaterial as desired in various embodiments.

At block 420, the temperature of the conductor or wire, whether or notit includes base insulation, may be controlled prior to extrusion. Forexample, one or more suitable preheaters or other devices may beutilized to control a pre-extrusion temperature. Multiple layers ofthermoplastic insulation may then be formed at block 425. For example,the first polymeric material may be utilized to extrude a first layer,and the second polymeric material may be utilized to form a secondlayer. A wide variety of suitable techniques may be utilized to extrudethe first and second layers of polymeric insulation as desired invarious embodiments. For example, at block 430, multiple layers ofpolymeric insulation may be co-extruded onto the wire. In other words,first and second layers may be co-extruded. As another example, at block435, multiple layers of polymeric insulation may be successivelyextruded onto the wire. In other words, a first layer may be extruded,and a second layer may be subsequently extruded over the first layer.Any suitable extrusion device and/or combination of extrusion devicesmay be utilized to extrude the multiple layers of thermoplasticinsulation. The temperature of the magnet wire and extruded insulationmay then be controlled at block 440 following extrusion. For example, acooling trough and/or other suitable components may be utilized to coolthe magnet wire following extrusion.

In certain embodiments, the method 400 may end following block 440. Inother embodiments, one or more additional operations may be performed.For example, in certain embodiments, one or more additional insulationlayers (e.g., another extruded layer, a conformal layer, etc.) may beformed on the magnet wire. As another example, the magnet wire may beformed into one or more articles (e.g., coils, hairpins, etc.) that maybe incorporated into an electrical appliance. The method 400 may thenend following the additional operations.

The operations described and shown in the method 400 of FIG. 4 may becarried out or performed in any suitable order as desired in variousembodiments. Additionally, in certain embodiments, at least a portion ofthe operations may be carried out in parallel. Furthermore, in certainembodiments, less than or more than the operations described in FIG. 4may be performed.

EXAMPLES

As set forth above, a wide variety of suitable polymeric materials maybe utilized to form co-extruded magnet wire insulation. For example, awide variety of suitable polymeric materials may be utilized to form thefirst layer 115 and the second layer 120 of the magnet wire 100 of FIG.1 . The examples set forth in Tables 1 and 2 below are intended asillustrative and non-limiting, and represent specific embodiments of thepresent disclosure in which certain example polymeric materials areutilized to form co-extruded magnet wire insulation. The wire samplesdiscussed in the examples of Table 1 were all prepared as rectangularwire having a conductor width of approximately 3.384 mm and a conductorthickness of approximately 1.834 mm with a tolerance of +/−0.015 mm. Theconductors were formed from oxygen free copper. Additionally, baseinsulation was formed from polyamideimide (“PAI”). The wire samplesdiscussed in the examples of Table 2 were all prepared as rectangularwire having a conductor width of approximately 0.386 inches(approximately 9.80 mm) and a conductor thickness of approximately 0.150inches (approximately 3.81 mm). The conductors were formed fromaluminum, and no base insulation was formed on the conductors prior toextrusion. In other embodiments, conductors may be formed from anysuitable materials having any suitable dimensions. Additionally, anysuitable base insulation may be utilized as desired or alternatively, nobase insulation may be included.

With reference to Table 1, a few example co-extruded wire samples areprovided. In particular, a first co-extruded sample includes a firstextruded layer of PEI and a second extruded layer of PEEK formed overthe PEI. A second co-extruded sample includes a first extruded layer ofPPSU and a second extruded layer of PAEK formed over the PPSU.Additionally, control samples of extruded single material PEEK, PPSU(e.g., Radel 5800), and PEI (e.g. Ultem 1000) are provided forcomparison to the co-extruded samples. A total thickness of the extrudedinsulation system is provided for each sample. For each co-extrudedsample, approximately equal thicknesses of the two materials (i.e., thefirst and second layers) were formed. Additionally, measured performancecriteria for the extruded samples are provided. First, measured PDIVvalues at room temperature are provided. Dielectric breakdown valuesdetermined utilizing a shotbox test are also provided. In a shotboxtest, a magnet wire is submerged in shot balls and tested until failure.

TABLE 1 Comparative Samples of Co-extruded Magnet Wire Co-extrudedCo-extruded Formulation PPSU PEI PEEK PEI/PEEK PPSU/PAEK Thickness 354324 182 280 250 (μm) PDIV Vp 1764 1513 1201 2758 2248 (room temperature)DB Shotbox 12636 16046 11734 11480 13940 Volts

As shown in Table 1, certain co-extruded insulation systems may providesimilar or better performance than conventional single polymer extrudedmaterials (e.g., PEEK, PPSU, PEI, etc.). For example, certainco-extruded insulation systems may provide enhanced PDIV and/ordielectric breakdown performance. As shown, the co-extruded PEI/PEEK andPPSU/PAEK samples exhibited much higher PDIV values than single polymerextruded samples. Indeed, the co-extruded samples exhibited improvedPDIV relative to single polymer samples (e.g., PPSU, PEI, etc.) thatwere much thicker than the co-extruded samples. Further, the dielectricbreakdown voltage of the co-extruded samples were similar to or betterthan single polymer extruded samples. It is noted that the singlepolymer samples illustrating higher dielectric breakdown values havethicker insulation than the co-extruded samples, which leads to higherdielectric breakdown voltage. Comparative single polymer samples withsimilar insulation thicknesses would have lower dielectric breakdownvoltages. Further, the co-extruded samples were found to have higher orimproved chemical resistance relative to the single polymer samplesutilizing PEI and PPSU. Additionally, the use of certain co-extrudedinsulation systems may reduce overall insulation costs relative toconventional single polymer materials.

With reference to Table 2, a few example co-extruded wire samples thatinclude different thickness ratios of first and second extruded layersare provided. In particular, a first co-extruded sample includes a firstextruded layer of PPSU and a second extruded layer of PEEK formed overthe PPSU. The ratio of the PPSU/PEEK thicknesses is approximately 75/25.A second co-extruded sample also includes a first extruded layer of PPSUand a second extruded layer of PEEK formed over the PPSU. The ratio ofthe PPSU/PEEK thicknesses is approximately 55/45. Additionally, threedifferent control samples of extruded single material PEEK are providedfor comparison to the co-extruded samples. A total thickness of theextruded insulation system is provided for each sample. Additionally,measured performance criteria for the extruded samples are provided.First, measured PDIV values at room temperature are provided. Dielectricbreakdown values determined utilizing a shotbox test are also provided.

TABLE 2 Comparative Samples of Co-extruded Magnet Wire PEEK PEEK PEEKCo-extruded Co-extruded Formulation #1 #2 #3 PPSU/PEEK PPSU/PEEKThickness Ratio N/A N/A N/A 75/25 55/45 Thickness (μm) 155 120 160 112166 PDIV Vp 1820 1679 1905 1602 1758 (room temperature) DB Shotbox 135309478 12093 4733 9250 Volts

As shown in Table 2, the co-extruded insulation systems that includePEEK over another extruded material provide similar performance toconventional insulation that only includes PEEK. It is noted that thefirst co-extruded sample was formed with a smaller thickness thanseveral of the control samples of PEEK. Given a higher thickness, thePDIV of the second sample would be increased and would likely becomparable to the thicker PEEK samples. Additionally, the dielectricshotbox test measures the dielectric strength at the thinnest area ofinsulation. Given the novelty of the co-extrusion process utilized toform the co-extruded samples, some relatively thin areas of insulationwere included in the samples, thereby leading to lower dielectricstrength measurements. As the co-extrusion process is improved andoptimized, wire can be formed with better concentricity, therebyimproving the dielectric strength of the co-extruded insulation.Additionally, even given the unoptimized manufacturing process, it isnoted that the 55/45 co-extruded sample had a dielectric strengthcomparable to the PEEK samples. Therefore, it was observed and can beconcluded that magnet wire formed with PEEK over a lower cost and lowerperformance material (e.g., PPSU, etc.) may have a similar PDIV anddielectric breakdown performance as conventional magnet wire that onlyincludes PEEK. Provided that a threshold thickness ratio ofhigh-performance material (e.g., PEEK) is provided, desired overallinsulation performance may be achieved with a co-extruded magnet wire.However, the overall cost of the insulation system and the magnet wiremay be reduced relative to conventional magnet wire that only includesextruded PEEK insulation.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments could include, while other embodiments do not include,certain features, elements, and/or operations. Thus, such conditionallanguage is not generally intended to imply that features, elements,and/or operations are in any way required for one or more embodiments orthat one or more embodiments necessarily include logic for deciding,with or without user input or prompting, whether these features,elements, and/or operations are included or are to be performed in anyparticular embodiment.

Many modifications and other embodiments of the disclosure set forthherein will be apparent having the benefit of the teachings presented inthe foregoing descriptions and the associated drawings. Therefore, it isto be understood that the disclosure is not to be limited to thespecific embodiments disclosed and that modifications and otherembodiments are intended to be included within the scope of the appendedclaims. Although specific terms are employed herein, they are used in ageneric and descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. A magnet wire comprising: a conductor; andextruded insulation formed around the conductor, the extruded insulationcomprising: a solid first layer formed around and bonded to theconductor from a first thermoplastic polymeric material having a firstthermal index and comprising at least one of polyester, nylon,polyphenylene sulfide, or polyphenylsulfone, the first layer comprisingat least fifty-five percent of a thickness of the extruded insulation;and a solid second layer formed around the first layer and in contactwith an entire outer periphery of the first layer, the second layerformed from a second thermoplastic polymeric material having a secondthermal index higher than the first thermal index and comprising atleast one of polyetheretherketone, polyaryletherketone, orpolyetherketoneketone, wherein the extruded insulation has a partialdischarge inception voltage of at least 1200 volts.
 2. The magnet wireof claim 1, wherein the first layer comprises between fifty-five percentand eighty percent of the thickness of the extruded insulation and thesecond layer comprises between twenty percent and forty-five percent ofthe thickness.
 3. The magnet wire of claim 1, wherein the thickness ofthe insulation is between 15 micrometers and 200 micrometers.
 4. Themagnet wire of claim 1, wherein a thickness of the insulation is between250 micrometers and 600 micometers.
 5. The magnet wire of claim 1,wherein the second thermoplastic polymeric material comprisespolyetherketoneketone.
 6. The magnet wire of claim 1, wherein the firstthermal index is 200° C. or less and the second thermal index is 220° C.or more.
 7. The magnet wire of claim 1, wherein the first thermal indexis 200° C. or less and the second thermal index is 240° C. or more. 8.The magnet wire of claim 1, wherein the first thermoplastic polymericmaterial comprises an amorphous material and the second thermoplasticpolymeric material comprises a semi-crystalline or a crystallinematerial.
 9. The magnet wire of claim 1, further comprising: a fillermaterial incorporated into one of the first thermoplastic polymericmaterial or the second thermoplastic polymeric material.
 10. The magnetwire of claim 9, wherein the filler material comprises at least one oftitanium dioxide, chromium dioxide, silica dioxide, or boron nitride.11. A magnet wire comprising: a conductor; and extruded insulationformed around the conductor, the extruded insulation comprising: a solidfirst layer formed around the conductor from a first thermoplasticpolymeric material having a first thermal index and comprising at leastone of polyester, nylon, polyphynylene sulfide, or polyphenylsulfone,the first layer comprising at least fifty-five percent of a thickness ofthe extruded insulation; and a solid second layer formed around thefirst layer and in contact with an entire outer periphery of the firstlayer, the second layer formed from a second thermoplastic polymericmaterial having a second thermal index higher than the first thermalindex and comprising polyetherketoneketone, wherein a thickness of theextruded insulation is between 15 micrometers and 200 micrometers. 12.The magnet wire of claim 11, wherein the first layer comprises betweenfifty-five percent and eighty percent of a thickness of the extrudedinsulation and the second layer comprises between twenty percent andforty-five percent of the thickness.
 13. The magnet wire of claim 11,wherein the first thermoplastic polymeric material comprises at leastone of polyester, nylon, polyphenylene sulfide, or polyphenylsulfone.14. The magnet wire of claim 11, wherein the first thermal index is 200°C. or less and the second thermal index is 220° C. or more.
 15. A magnetwire comprising: a conductor; and extruded insulation formed around theconductor, the extruded insulation comprising: a first layer formedaround the conductor from a first thermoplastic polymeric materialhaving a first thermal index, the first polymeric material comprising atleast one of polyester, nylon, polyphenylene sulfide, orpolyphenylsulfone, the first layer comprising at least fifty-fivepercent of a thickness of the extruded insulation; and a second layerformed around the first layer and in contact with an entire outerperiphery of the first layer, the second layer formed from a secondthermoplastic polymeric material having a second thermal index higherthan the first thermal index, the second polymeric material comprisingat least one of polyetheretherketone, polyaryletherktone, orpolyetherketoneketone, wherein a thickness of the extruded insulation isbetween 250 micrometers and 600 micrometers.
 16. The magnet wire ofclaim 15, wherein the first layer comprises between fifty-five percentand eighty percent of the thickness of the extruded insulation and thesecond layer comprises between twenty percent and forty-five percent ofthe thickness.
 17. The magnet wire of claim 15, wherein the firstthermal index is 200° C. or less and the second thermal index is 220° C.or more.